Update fetchsvn for proxy support

svn path=/nixpkgs/trunk/; revision=15654

pkgs/build-support/fetchsvn/builder.sh

@@ -6,6 +6,18 @@ if test "$sshSupport"; then
     export SVN_SSH="$openssh/bin/ssh"
 fi
 
+if test -n "$http_proxy"; then
+    # Configure proxy
+    mkdir .subversion
+    proxy="${http_proxy#*://}"
+
+    echo '[global]' > .subversion/servers
+    echo "http-proxy-host = ${proxy%:*}" >> .subversion/servers
+    echo "http-proxy-port = ${proxy##*:}" >> .subversion/servers
+
+    export HOME="$PWD"
+fi;
+
 # Pipe the "p" character into Subversion to force it to accept the
 # server's certificate.  This is perfectly safe: we don't care
 # whether the server is being spoofed --- only the cryptographic

pkgs/build-support/fetchsvn/default.nix

@@ -11,4 +11,12 @@ stdenv.mkDerivation {
   outputHash = if sha256 == "" then md5 else sha256;
   
   inherit url rev sshSupport openssh;
+
+  impureEnvVars = [
+    # We borrow these environment variables from the caller to allow
+    # easy proxy configuration.  This is impure, but a fixed-output
+    # derivation like fetchurl is allowed to do so since its result is
+    # by definition pure.
+    "http_proxy" "https_proxy" "ftp_proxy" "all_proxy" "no_proxy"
+    ];
 }